We were all very patient while they rolled out two-factor authentication. It took much longer than we all expected, but now it's clear why — they were launching that with an entirely new set of servers. And along with that, they reportedly implemented an improved development process for new features and functionality. If this is effective, it should translate into quicker roll-outs of new features and enhancements.

I build and maintain rather complex systems, so I know how overwhelming it can be to move a large and complex system forward while thousands of people are using it every minute of every day. There's just no margin for error, and I've observed Runbox being extremely cautious with the roll-out of their new systems. I appreciate that greatly, so they have my patience.

I have a long list of fixes and improvements that I'd like to see, and Push for IMAP is definitely something that would be good to have.

AFAIK FastMail solution is not a third party. They just managed to get Apple to issue an authentification certificate for them, and the rest of the protocol is described for dovecot.

From the FastMail blog regarding Mail on iOS:

"Upon seeing that the IMAP server offers support for Apple's push mechanism, the app sends the server a list of folders that its interested in knowing about changes for, and a push token. Just as described above, when something changes the IMAP server sends a message through Apple's push service, which causes the Mail app to wake and make IMAP requests to get the changes."

"...there's arguably a privacy concern in that we're sending fragments of mail contents through a third-party service (though you already have to trust Apple if you're using their hardware so it's perhaps not a concern)."

I think as they say above, if you opted in to Apple's system, and can always choose "Fetch" instead of "Push", then really it is up to the customer how they handle this.

As I said, it is a popular request, so we will look seriously at what we can do here for customers.

"Upon seeing that the IMAP server offers support for Apple's push mechanism, the app sends the server a list of folders that its interested in knowing about changes for, and a push token. Just as described above, when something changes the IMAP server sends a message through Apple's push service, which causes the Mail app to wake and make IMAP requests to get the changes."

"...there's arguably a privacy concern in that we're sending fragments of mail contents through a third-party service (though you already have to trust Apple if you're using their hardware so it's perhaps not a concern)."

I think as they say above, if you opted in to Apple's system, and can always choose "Fetch" instead of "Push", then really it is up to the customer how they handle this.

As I said, it is a popular request, so we will look seriously at what we can do here for customers.